Electric continuous-flow heater with water deficiency protection and safety switch



Feb. 28, 1961 L. SCHOMANN ELECTRIC CONTINUOUS-FLOW HEATER WITH WATER DEFICIENCY PROTECTION AND SAFETY SWITCH Filed Dec. 15, 1958 INVENTOR.

flamfa/ovu M8, mm \7 U D. I w m w r n w j 7H. W L N WW" wm I z 3 United States Patent ELECTRIC CONTINUOUS-FLOW HEATER WITH WATER DEFICIENCY PROTECTION AND SAFETY SWITCH Leonid Schoruann, Langenberg, Rhineland, Germany, assignor to Alfred Eckerfeld, Essen, Ruhr, Germany Filed Dec. 15, 1958, Ser. No. 780,436 Claims priority, application Germany Dec. 14, 1957 46 Claims. c1. 219-39 This invention relates to electric continuous-flow heaters having an electric heating coil arranged in the flow passage around which a liquid to be heated circulates. It has already been suggested that, with this kind of continuous-flow heater, two series connected contact springs be arranged in the circuit of the heating coil and that each be actuated by a particular diaphragm switch, whereby one of the diaphragm switches responds as a water deficiency safety device through a pressure differential formed across a throttling point which is caused by the The invention has for its object the improvement of such an -arrangement. In particular, it is an object to design the second diaphragm switch so that it functions as a non-retarding safety switch. In accordance with theinvention, this object is attained by providing a structure where the heating channels 5, as enumerated in the drawing described more fully below, directly open into the overpressure chamber 7 of the second diaphragm switch 11, and a section 6" of the heating coil protrudes into this overpressure chamber 7, so that the second diaphragm switch 11 will respond as a safety switch independently of the water deficiency safety device. Through this arrangement of the second diaphragm switch. the switching off of it is achieved that the heating power is immediately accomplished if any overpressure occurs through steam formation in the heating channels, since such an overpressure is then directly transmitted to the diaphragm chamber of the safety switch. Switching off the heating coil must take place Within a fraction of a second in order to avoid the burning out of the heating coil through overload. A heat sensing element arranged in the flow passage would only re-act to slow overheating and not to steam formation, and therefore, the safety switchwould then be actuated much too late.

The invention can behest accomplished by constructing the diaphragm 11 of the safety switch as a pre-formed bimetallic diaphragm, and so arranging it that it responds both to overpressure and to excessive heat by actuating the contact spring 27 and causing it to open.

s In order to. avoid any unintentional switching on of the heating coil, a further improvement of the invention is'provided in-theform of a structure where the safety switch 11 responds to overpressure by operating the contactspring 27 through the transmission member 25, and wherein a self-acting locking device 32 is releasable through which the contact spring 27 is arrested inits switched-0d position. After the safety switch has so responded,'the lock must first be released by hand before the apparatus can again be put into operation.

simplified 'construction of the apparatus may be 2,973,424 Patented Feb 28, 1961 ice achieved by structurally assembling the water deficiency safety device with the safety switch and in such manner that both diaphragm switches 11, 10 are arranged coaxially with each other in a common casing 19, 19, and where both motion transmission members 25, 28 are arranged transversely to the direction of movement of the diaphragm 10, 11 and emerge from the casing 19, 19.

An embodiment of the invention is described in detail in the following description and drawings wherein:

Fig. 1 is a front view of the continuous-flow heater,

Fig. 2 is a section taken at line IIII of Fig. 1,

Fig. 3 is a longitudinal section taken at line III-III of Fig. 1,

Fig. 4 is a section taken at line IV-IV of Fig. 3, and Fig. 5 shows a section taken at line VV of Fig. 3.

In a base element 1 made from insulating plastic material an inlet channel 3 is arranged which is connected to an inlet connection 2 and into which an adjustable throttle screw 4 projects. A heating channel 5 of large cross section is connected to the outlet channel 3, and has arranged therein a heating coil 6. The heating channel 5 opens into a chamber 7 in the base element 1. From chamber 7 a further heating channel 5' which encloses a heating coil 6 leads to an outlet channel 8 which ends in an outlet connection 9. The heating channels 5, 5 and the heating coil connected to the terminals 17, 17 are in an insert 18 which can be removed from the base element 1.

The chamber 7 is closed by means of a preformed bimetallic diaphragm 11 so that the chamber 7 operates; as an overpressure chamber of a diaphragm switch. A portion 6 of the heating coil 6, 6' projects into the space 7. The bimetallic diaphragm is held in place by a diaphragm casing 19 part of which encloses and seals a second pre-formedmetallic diaphragm. Between the two diaphragms 10, 11 there is a diaphragm chamber 20 which is connected by a connecting channel 21 to the inlet channel 3 in front of the throttle screw 4. The diaphragm casing section 19 has mounted thereon by means of screw 23 a casing cap 19 which defines an outer diaphragm chamber 22. The outer diaphragm chamber 22 is connected by means of a connecting channel 24 to the outer channel 8. I

A transmission member 25 extending transversely to the movement of the diaphragm is supported on the diaphragm 11 and emerges laterally from the diaphragm casing section 19. This transmission member 25 is connected with the casing section 19 by means of an elastic plastic tube 25' which serves as a sealing means for the diaphragm chambers. The transmission member 25 lies upon an insulation bridge 26 which mechanically connects two contact springs mounted on the base element with each other}. In similar manner, a transmission member 28 supported by the diaphragm 10 emerges from the casing cap 19' and lies-on an insulation bridge 29 of a further pair of contact springs. The contact springs 27, 30 are connected in series in the circuit of the heating coilf6, 6', 6" and cooperate withfixed counter contacts 31, 31. On the front of the tranmission member 25 a resilient tongue 32 is mounted on the base element 1 .is as follows. Normally, the. pre-formed bimetallic diaphragm .11 remains in the positionshow'n and in which the transmission member 25 is somewhat raised from the insulation bridge 26 so that the contact springs 27 lie on the counter contacts 31 under the influence of their own spring force. As long as no water flows through the apparatus, the diaphragm and the transmission member 28 maintain the position as shown in which the contact springs 30 do not make contact with the countercontact 31. The current circuit of the heating coil 6, 6' is therefore not closed.

Immediately upon the opening of a tap valve, not

depicted, water flows through the apparatus and as a result of the throttlingat 4, a pressure difference exists in the diaphragm chambers to 22 so that the diaphragm 10 is curved upwards. Therefore, by means of the trans mission member 28 the heating current circuit is bipolarly closed between the contact springs 30 and the counter contacts 31 so that the water flowing through is heated. However, should overpressure result in the heating channels 5, 5 and in the chamber 7 through steam formation, the diaphragm 1.1 is pushed upwards, and, by means of the transmission member the contact springs 27, is raised from the counter-contact 31' and the circuit interrupted. The diaphragm responds in a similar manner if the water present in space 7 reaches too high a temperature, inasmuch as the bimetallic diaphragm also reacts to a raise in temperature.

As soon as the bimetallic diaphragm 11, whether by overpressure or overheating, is made to respond, the transmission member 25 is moved into the switched-off position. The spring tongue 32 locks the transmission member in this position so that the apparatus can only be taken back into operation when, after the cause of the trouble has been removed, the spring tongue 32 is pressed to the side by hand, thereby again releasing the transmission member.

I claim:' I

1. An electric continuous-flow heater comprising in combination a housing having liquid inlet and outlet; a

liquid flow passage connecting said inlet with said outlet comprising an inlet channel, a heating channel, an overpressure chamben and an outlet channel; an adjustable throttle connected in one of said channels; a heater element mounted in said heating channel having a portion thereof extending into said over-pressure chamber, said heating channel being connected with said over-pressure chamber; a first diaphragm switch mounted in said housing comprising a diaphragm, a pair of normally open electrical contacts, and coupling means between said diaphragm and said contacts, said diaphragm being responsive to a pressure differential in said flow passage between two points one at each side of said throttle for closing said contacts upon the formation of said pressure differential; a second diaphragm switch mounted in said housing comprising a diaphragm mounted in a wall of said over-pressure chamber, a pair of normally closed electrical contacts, and means for coupling said diaphragm with said electrical contacts, said second diaphragm switch being arranged to become open upon an excessive pressure increase in said over-pressure chamber; said first diaphragm switch, said second diaphragm switch and said heater element being series-connected electrically; whereby the flow of liquid in said liquid flow passage causes said first diaphragm switch to be closed, and' whereby the pressure of vapor formed in said overpressure chamber caused by aliquid deficiency in said liquid flow passage causes "the instantaneous opening of said second diaphragm switch.

2. An, electr iccontinuous-flow heater comprising in combination a housing having liquid inlet and outlet; a

liquid flow passage connectingv said inlet with said outlet comprising an inlet channel, a heating channel, an overpressure chamber, and an outlet channel, an adjustable throttle connected in -said-inlet .channel; a heating element mounted. in said heating channel having a portion thereof'extending 'intosaid over-pressure chamber, said heating channel being connected with said over-pressure chamber; a first diaphragm switch mounted in said housing comprising a diaphragm, a pair of normally open electrical contacts, and coupling means between said diaphragm and said contacts, said diaphragm being responsive to a pressure differential in said flow passage between two points one at each side of said throttle for closing said contacts upon the formation of said pressure differential; and a second diaphragm switch mounted in said housing comprising a pre-formed bi-metallic diaphragm mounted in a wall of said over-pressure chamber, a pair of normally closed electrical contacts, and means for coupling said diaphragm with said electrical contacts, the bi-metallic elements of said diaphragm being so arranged'that an abnormal increase in temperature of said water causes said bi-metallic diaphragm to open said electrical contacts, said second diaphragm switch additionally being so arranged to become open upon the formation of an excessive pressure increase in said overpressure chamber; said first diaphragm switch, said second diaphragm switch and said heater element being series-connected electrically; whereby the flow of water through said water flow passage causes the circuit to said meter element to be closed, and whereby either the overheating of water in said water flow passage or a water deficiency in said liquid flow passage causes the circuit to said heater element to be opened.

3. An electric continuous-flow heater according to claim 2, and further having a releasable self-acting locking means mounted in said housing and cooperating with said second diaphragm switch, whereby the operation of said second diaphragm switch causes said locking means to lock the contact springs associated with said switch in the open position. 1

4. An electric continuous-flow heater according to claim 3 wherein the means for coupling the diaphragm of said second diaphragm switch with the electrical contacts associated with said switch comprises a movement transmission member pivotally arranged with respect to the direction of movement of the diaphragm, said locking means comprising a spring member having a tongue lying .in the switched-on position on the front of said transmission member and sliding over the end of said transmission member and preventing any return movement of said transmission member when said member has reached the switched oif position.

5. An electric continuous-flow heater comprising in combination a housing having liquid inlet and outlet; a liquid flow passage connecting said inlet with said outlet comprising an inlet channel, a heating channel, an over-pressure chamber, and an outlet channel, an adjustable throttle being connected in said inlet channel; a

heater element mounted in said heating channel having a portion thereof extending into said over-pressure chamber, said heating channel being connected with said overpressure chamber; a first diaphragm switch mounted in said housing comprising a diaphragm, a pair of normally open electrical contacts, and a movement transmission member coupling said diaphragm with said contacts, said diaphragm being responsive to a pressure diflerential in said flow passage between two points one at each side'of said throttle for closing said'contacts upon the formation of said pressure difierential; and a second diaphragm switch mounted in said housing comprising a diaphragm mounted in a wall of said over-pressure chamber, a pair of normally closed electrical contacts, and a movement transmission member for coupling said diaphragm with said electrical contacts, both' movement transmission members being arranged transversely to the direction of movement of said diaphragms and leading out of said housing; both diaphragm switches being arranged coaxiallyto each other; said second diaphragm switch being arranged to become open upon an excessive pressure increase in said over-pressure chamber; and said first diaphragm switch, said second diaphragm switch, and

said heater element being series-connected electrically; whereby the flow of liquid in said liquid flow passage closes said first diaphragm switch, and whereby the pressure of vapor formed in said over-pressure chamber caused by a liquid deficiency in said liquid flow passage causes the instantaneous opening of said second diaphragm switch.

6. An electric continuous-flow heater according to claim 5 wherein a portion of said housing is separated by said two diaphragms to define three consecutive diaphragm chambers, the middle one of said three diaphragm References Cited in the file of this patent UNITED STATES PATENTS Hulse Sept. 22, 1925 Antonelli Jan. 28, 1930 

